Apparatus and method for measuring vehicle position based on low frequency signals

ABSTRACT

A position alignment method performed by a ground assembly for wireless power transfer includes measuring, through at least one low frequency (“LF”) receiver of the ground assembly, a first magnetic flux density for a magnetic field emitted from at least one LF transmitter of a vehicle assembly; measuring, through the at least one LF receiver, a second magnetic flux density for a magnetic field emitted from the at least one LF transmitter; configuring a received signal measurement based on a comparison result of the first magnetic flux density and the second magnetic flux density; and providing the configured received signal measurement to a vehicle.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims under 35 U.S.C. § 119(a) the benefit of KoreanPatent Applications No. 10-2018-0131788 filed on Oct. 31, 2018 and No.10-2019-0128043 filed on Oct. 15, 2019 in the Korean IntellectualProperty Office (KIPO), the entire contents of which are incorporatedherein by reference.

BACKGROUND (a) Technical Field

The present disclosure relates to a method for measuring a position forwireless charging and an apparatus using the same, amore particularly,to the method for measuring the position by using low frequency (LF)signals, and the apparatus using the same.

(b) Description of the Related Art

An electric vehicle (EV) drives an electric motor by power of a battery,and produces less air pollution such as exhaust gas and noise comparedwith a conventional gasoline engine vehicle, and has other benefits suchas a longer life and simplified operation thereof.

EVs are classified into hybrid electric vehicles (HEVs), plug-in hybridelectric vehicles (PHEVs), and electric vehicles (EVs), depending on adriving source. The HEV has an engine as a main power source and a motoras an auxiliary power source. The PHEV has a main power motor and anengine used when a battery is discharged. The EV has a motor, but itdoes not have an engine.

Wireless charging of the battery for driving the electric motor of theEV may be performed by coupling a primary coil of a charging stationwith a secondary coil of the EV in a magnetic resonance manner.Additionally, in a magnetic resonance wireless power transfer (WPT)system, if the primary and secondary coils are not aligned, theefficiency of the WPT may be reduced substantially. Therefore, thealignment of the primary coils and the secondary coils is required.

As a conventional alignment scheme, there is a technique of aligning anEV equipped with a secondary coil to a primary coil of a ground assembly(GA) using a rear camera. Another technique involves moving a movablecharging pad after an EV is parked in a parking area by a bump to aligna primary coil of the charging pad with a secondary coil of the EV.

However, such conventional techniques may require a user's interventionin the alignment of the coils, and thus inconvenience due to the user'sintervention, and result in a substantial deviation of the alignment,which may lead to excessive system performance deterioration due toslight coil misalignment. Therefore, in the magnetic resonance WPTsystem sensitive to the misalignment of the coils, it is difficult torealize optimal power transfer efficiency, and the stability andreliability of the system may be deteriorated.

Accordingly, there is a need for a method of accurately measuring orestimating the position of a vehicle for alignment between a groundassembly of a charging station and a vehicle assembly of the vehicle inthe WPT system.

SUMMARY

The present disclosure provides a position alignment method for wirelesspower transfer, which is performed in a ground assembly. Additionally,the present disclosure provides a position measurement apparatus forwireless power transfer, which is performed in a vehicle assembly.Additionally, the present disclosure provides a position measurementapparatus using the position measurement method.

According to exemplary embodiments of the present disclosure, a positionalignment method performed by a GA for wireless power transfer maycomprise measuring, through at least one LF receiver of the GA, a firstmagnetic flux density for a magnetic field emitted from at least one LFtransmitter of a vehicle assembly (VA); measuring, through the at leastone LF receiver, a second magnetic flux density for a magnetic fieldemitted from the at least one LF transmitter; configuring a receivedsignal measurement based on a comparison result of the first magneticflux density and the second magnetic flux density; and providing theconfigured received signal measurement to a vehicle.

The first magnetic flux density may be a maximum magnetic flux densityfor the magnetic field emitted from the at least one LF transmitter, andthe second magnetic flux density may be a minimum magnetic flux densityfor the magnetic field emitted from the at least one LF transmitter.

The configuring of the received signal measurement may comprisedetermining whether a difference between the first magnetic flux densityand the second magnetic flux density is greater than or equal to athreshold; and excluding the first magnetic flux density and the secondmagnetic flux density from the received signal measurement when thedifference between the first magnetic flux density and the secondmagnetic flux density is less than the threshold.

The received signal measurement may be a received signal strengthindicator (RSSI).

The first magnetic flux density and the second magnetic flux density maybe measured at different time points by the at least one LF receiver.

The position alignment method may further comprise initially detecting amagnetic field emitted from the at least one LF transmitter of the VA.

Further, according to exemplary embodiments of the present disclosure, aposition measurement method performed by a VA for wireless powertransfer may comprise emitting a magnetic field having a first magneticflux density through at least one LF transmitter; emitting a magneticfield having a second magnetic flux density through the at least one LFtransmitter; receiving a received signal measurement from a GA thatdetects the first magnetic flux density and the second magnetic fluxdensity; and calculating a distance between the VA and the GA based onthe received signal measurement.

The first magnetic flux density may be a maximum magnetic flux densityfor the magnetic field emitted from the at least one LF transmitter, andthe second magnetic flux density may be a minimum magnetic flux densityfor the magnetic field emitted from the at least one LF transmitter.

The received signal measurement may include only data related to thefirst magnetic flux density and the second magnetic flux density whichhave a difference equal to or greater than a threshold.

The received signal measurement may be an RSSI.

The first magnetic flux density and the second magnetic flux density maybe emitted at different time points.

The position measurement method may further comprise initially emittinga magnetic field through the at least one LF transmitter.

Further, according to exemplary embodiments of the present disclosure, aposition measurement apparatus may comprise at least one low frequency(LF) transmitter; a communication module configured to receive areceived signal measurement from a ground assembly (GA) that detects thefirst magnetic flux density and the second magnetic flux density; and aprocessor configured to control the LF transmitter to emit a magneticfield having a first magnetic flux density and to emit a magnetic fieldhaving a second magnetic flux density, and calculate a distance betweena vehicle assembly (VA) and the GA based on the received signalmeasurement.

The first magnetic flux density may be a maximum magnetic flux densityfor the magnetic field emitted from the at least one LF transmitter, andthe second magnetic flux density may be a minimum magnetic flux densityfor the magnetic field emitted from the at least one LF transmitter.

The received signal measurement may include only data related to thefirst magnetic flux density and the second magnetic flux density whichhave a difference equal to or greater than a threshold.

The received signal measurement may be an RSSI.

The first magnetic flux density and the second magnetic flux density maybe emitted at different time points.

The processor may be further configured to initially emit a magneticfield through the at least one LF transmitter.

The first magnetic flux density and the second magnetic flux density maybe measured for each magnetic field emitted by the at least one LFtransmitter by each of at least one LF receiver of an electric vehiclesupply equipment (EVSE).

The LF receiver may be an LF antenna or an LF sensor.

According to the exemplary embodiments of the present disclosure, byaccurately measuring the position of the vehicle using the LF signals,the primary coil of the ground assembly and the secondary coil of theelectric vehicle can be precisely aligned, thereby maximizing wirelesscharging efficiency.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure will become more apparent by describing in detailexemplary embodiments of the present disclosure with reference to theaccompanying drawings, in which:

FIG. 1 is a conceptual diagram illustrating a concept of a wirelesspower transfer (WPT) to which exemplary embodiments of the presentdisclosure are applied;

FIG. 2 is a conceptual diagram illustrating a WPT circuit according toexemplary embodiments of the present disclosure;

FIG. 3 is a conceptual diagram for explaining a concept of alignment inan EV WPT according to exemplary embodiments of the present disclosure;

FIG. 4 is a conceptual diagram illustrating position alignment forwireless charging to which exemplary embodiments of the presentdisclosure are applied;

FIGS. 5A and 5B are diagrams illustrating an example of LF antennaalignment between a transmission pad and a reception pad;

FIG. 6 is a diagram illustrating an error occurring when aligningpositions using LF signals or magnetic vectoring;

FIG. 7A is a diagram describing magnetic flux densities when atransmission coil and a reception coil are located within a very shortdistance according to an exemplary embodiment of the present disclosure;

FIG. 7B is a diagram describing magnetic flux densities when atransmission coil and a reception coil are located within a very shortdistance according to another exemplary embodiment of the presentdisclosure;

FIG. 8 is a diagram describing magnetic flux densities when a distancebetween a transmission coil and a reception coil is changed within avery close distance according to an exemplary embodiment of the presentdisclosure;

FIGS. 9A to 9C are sequence charts illustrating operations of a positionalignment method according to an exemplary embodiment of the presentdisclosure;

FIG. 10 is a block diagram illustrating a position measurement apparatusaccording to an exemplary embodiment of the present disclosure; and

FIG. 11 is a block diagram illustrating an EVSE according to anexemplary embodiment of the present disclosure.

It should be understood that the above-referenced drawings are notnecessarily to scale, presenting a somewhat simplified representation ofvarious features illustrative of the basic principles of the disclosure.The specific design features of the present disclosure, including, forexample, specific dimensions, orientations, locations, and shapes, willbe determined in part by the particular intended application and useenvironment.

DETAILED DESCRIPTION

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g., fuels derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example bothgasoline-powered and electric-powered vehicles.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. Throughout the specification, unless explicitly describedto the contrary, the word “comprise” and variations such as “comprises”or “comprising” will be understood to imply the inclusion of statedelements but not the exclusion of any other elements. In addition, theterms “unit”, “-er”, “-or”, and “module” described in the specificationmean units for processing at least one function and operation, and canbe implemented by hardware components or software components andcombinations thereof.

Further, the control logic of the present disclosure may be embodied asnon-transitory computer readable media on a computer readable mediumcontaining executable program instructions executed by a processor,controller or the like. Examples of computer readable media include, butare not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes,floppy disks, flash drives, smart cards and optical data storagedevices. The computer readable medium can also be distributed in networkcoupled computer systems so that the computer readable media is storedand executed in a distributed fashion, e.g., by a telematics server or aController Area Network (CAN).

Embodiments of the present disclosure are disclosed herein. However,specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing exemplary embodiments of thepresent disclosure, however, exemplary embodiments of the presentdisclosure may be embodied in many alternate forms and should not beconstrued as limited to exemplary embodiments of the present disclosureset forth herein. While describing the respective drawings, likereference numerals designate like elements.

It will be understood that although the terms “first,” “second,” etc.may be used herein to describe various components, these componentsshould not be limited by these terms. These terms are used merely todistinguish one element from another. For example, without departingfrom the scope of the present disclosure, a first component may bedesignated as a second component, and similarly, the second componentmay be designated as the first component.

It will be understood that when a component is referred to as being“connected to” another component, it can be directly or indirectlyconnected to the other component. That is, for example, interveningcomponents may be present. On the contrary, when a component is referredto as being “directly connected to” another component, it will beunderstood that there is no intervening components.

All terms including technical or scientific terms, unless being definedotherwise, have the same meaning generally understood by a person ofordinary skill in the art. It will be understood that terms defined indictionaries generally used are interpreted as including meaningsidentical to contextual meanings of the related art, unless definitelydefined otherwise in the present specification, are not interpreted asbeing ideal or excessively formal meanings.

Additionally, it is understood that one or more of the below methods, oraspects thereof, may be executed by at least one controller. The term“controller” may refer to a hardware device that includes a memory and aprocessor. The memory is configured to store program instructions, andthe processor is specifically programmed to execute the programinstructions to perform one or more processes which are describedfurther below. The controller may control operation of units, modules,parts, devices, or the like, as described herein. Moreover, it isunderstood that the below methods may be executed by an apparatuscomprising the controller in conjunction with one or more othercomponents, as would be appreciated by a person of ordinary skill in theart.

According to exemplary embodiments of the present disclosure, an EVcharging system may be defined as a system for charging a high-voltagebattery mounted in an EV using power of an energy storage device or apower grid of a commercial power source. The EV charging system may havevarious forms according to the type of EV. For example, the EV chargingsystem may be classified as a conductive-type using a charging cable ora non-contact wireless power transfer (WPT)-type (also referred to as an“inductive-type”). The power source may include a residential or publicelectrical service or a generator utilizing vehicle-mounted fuel, andthe like.

Additional terms used in the present disclosure are defined as follows.

“Electric Vehicle (EV)”: An automobile, as defined in 49 CFR 523.3,intended for highway use, powered by an electric motor that drawscurrent from an on-vehicle energy storage device, such as a battery,which is rechargeable from an off-vehicle source, such as residential orpublic electric service or an on-vehicle fuel powered generator. The EVmay be a four or more wheeled vehicle manufactured for use primarily onpublic streets or roads.

The EV may include an electric vehicle, an electric automobile, anelectric road vehicle (ERV), a plug-in vehicle (PV), a plug-in vehicle(xEV), etc., and the xEV may be classified into a plug-in all-electricvehicle (BEV), a battery electric vehicle, a plug-in electric vehicle(PEV), a hybrid electric vehicle (HEV), a hybrid plug-in electricvehicle (HPEV), a plug-in hybrid electric vehicle (PHEV), etc.

“Plug-in Electric Vehicle (PEV)”: An EV that recharges the on-vehicleprimary battery by connecting to the power grid.

“Plug-in vehicle (PV)”: An electric vehicle rechargeable throughwireless charging from an electric vehicle supply equipment (EVSE)without using a physical plug or a physical socket.

“Heavy duty vehicle (H.D. Vehicle)”: Any four-or more wheeled vehicle asdefined in 49 CFR 523.6 or 49 CFR 37.3 (bus).

“Light duty plug-in electric vehicle”: A three or four-wheeled vehiclepropelled by an electric motor drawing current from a rechargeablestorage battery or other energy devices for use primarily on publicstreets, roads and highways and rated at less than 4,545 kg grossvehicle weight.

“Wireless power charging system (WCS)”: The system for wireless powertransfer and control between the GA and VA including alignment andcommunications. This system transfers energy from the electric supplynetwork to the electric vehicle electromagnetically through a two-partloosely coupled transformer.

“Wireless power transfer (WPT)”: The transfer of electrical power fromthe alternating current (AC) supply network to the electric vehicle bycontactless means.

“Utility”: A set of systems which supply electrical energy and mayinclude a customer information system (CIS), an advanced meteringinfrastructure (AMI), rates and revenue system, etc. The utility mayprovide the EV with energy through rates table and discrete events.Additionally, the utility may provide information about certification onEVs, interval of power consumption measurements, and tariff.

“Smart charging”: A system in which EVSE and/or PEV communicate withpower grid to optimize charging ratio or discharging ratio of EV byreflecting capacity of the power grid or expense of use.

“Automatic charging”: A procedure in which inductive charging isautomatically performed after a vehicle is located in a proper positioncorresponding to a primary charger assembly that can transfer power. Theautomatic charging may be performed after obtaining necessaryauthentication and right.

“Interoperability”: A state in which components of a system interworkwith corresponding components of the system in order to performoperations aimed by the system. Additionally, informationinteroperability may refer to capability that two or more networks,systems, devices, applications, or components may efficiently share andeasily use information without causing inconvenience to users.

“Inductive charging system”: A system transferring energy from a powersource to an EV through a two-part gapped core transformer in which thetwo halves of the transformer, primary and secondary coils, arephysically separated from one another. In the present disclosure, theinductive charging system may correspond to an EV power transfer system.

“Inductive coupler”: The transformer formed by the coil in the GA Coiland the coil in the VA Coil that allows power to be transferred withgalvanic isolation.

“Inductive coupling”: Magnetic coupling between two coils. In thepresent disclosure, coupling between the GA Coil and the VA Coil.

“Ground assembly (GA)”: An assembly on the infrastructure side of the GACoil, a power/frequency conversion unit and GA controller as well as thewiring from the grid and between each unit, filtering circuits,housing(s) etc., necessary to function as the power source of wirelesspower charging system. The GA may include the communication elementsnecessary for communication between the GA and the VA.

“Vehicle assembly (VA)”: An assembly on the vehicle of the VA Coil,rectifier/power conversion unit and VA controller as well as the wiringto the vehicle batteries and between each unit, filtering circuits,housing(s), etc., necessary to function as the vehicle part of awireless power charging system. The VA may include the communicationelements necessary for communication between the VA and the GA. The GAmay be referred to as a supply device, and the VA may be referred to asan EV device.

“Supply device”: An apparatus which provides the contactless coupling tothe EV device. In other words, the supply device may be an apparatusexternal to an EV. When the EV is receiving power, the supply device mayoperate as the source of the power to be transferred. The supply devicemay include the housing and all covers.

“EV device”: An apparatus mounted on the EV which provides thecontactless coupling to the supply device. In other words, the EV devicemay be installed in the EV. When the EV is receiving power, the EVdevice may transfer the power from the primary to the EV. The EV devicemay include the housing and all covers.

“GA controller”: The portion of the GA which regulates the output powerlevel to the GA Coil based on information from the vehicle.

“VA controller”: The portion of the VA that monitors specific on-vehicleparameters during charging and initiates communication with the GA tocontrol output power level. The GA controller may be referred to as asupply power circuit (SPC), and the VA controller may be referred to asan electric vehicle (EV) power circuit (EVPC).

“Magnetic gap”: The vertical distance between the plane of the higher ofthe top of the litz wire or the top of the magnetic material in the GACoil to the plane of the lower of the bottom of the litz wire or themagnetic material in the VA Coil when aligned.

“Ambient temperature”: The ground-level temperature of the air measuredat the subsystem under consideration and not in direct sun light.

“Vehicle ground clearance”: The vertical distance between the groundsurface and the lowest part of the vehicle floor pan.

“Vehicle magnetic ground clearance”: The vertical distance between theplane of the lower of the bottom of the litz wire or the magneticmaterial in the VA Coil mounted on a vehicle to the ground surface.

“VA coil magnetic surface distance”: the distance between the plane ofthe nearest magnetic or conducting component surface to the lowerexterior surface of the VA coil when mounted. This distance includes anyprotective coverings and additional items that may be packaged in the VAcoil enclosure. The VA coil may be referred to as a secondary coil, avehicle coil, or a receive coil. Similarly, the GA coil may be referredto as a primary coil, or a transmit coil.

“Exposed conductive component”: A conductive component of electricalequipment (e.g., an electric vehicle) that may be touched and which isnot normally energized but which may become energized in case of afault.

“Hazardous live component”: A live component, which under certainconditions may generate a harmful electric shock.

“Live component”: Any conductor or conductive component intended to beelectrically energized in normal use.

“Direct contact”: Contact of persons with live components. (See IEC61440)

“Indirect contact”: Contact of persons with exposed, conductive, andenergized components made live by an insulation failure. (See IEC 61140)

“Alignment”: A process of finding the relative position of supply deviceto EV device and/or finding the relative position of EV device to supplydevice for the efficient power transfer that is specified. In thepresent disclosure, the alignment may direct to a fine positioning ofthe wireless power transfer system.

“Pairing”: A process by which a vehicle is correlated with the uniquededicated supply device, at which it is located and from which the powerwill be transferred. Pairing may include the process by which a VAcontroller and a GA controller of a charging spot are correlated. Thecorrelation/association process may include the process of associationof a relationship between two peer communication entities.

“High-level communication (HLC)”: HLC is a special type of digitalcommunication. HLC is necessary for additional services which are notcovered by command & control communication. The data link of the HLC mayuse a power line communication (PLC), but it is not limited.

“Low-power excitation (LPE)”: LPE means a technique of activating thesupply device for the fine positioning and pairing so that the EV maydetect the supply device, and vice versa.

“Service set identifier (SSID)”: SSID is a unique identifier consistingof 32-characters attached to a header of a packet transmitted on awireless LAN. The SSID identifies the basic service set (BSS) to whichthe wireless device attempts to connect. The SSID distinguishes multiplewireless LANs. Therefore, all access points (APs) and allterminal/station devices that want to use a specific wireless LAN mayuse the same SSID. Devices that do not use a unique SSID are not able tojoin the BSS. Since the SSID is shown as plain text, it may not provideany security features to the network.

“Extended service set identifier (ESSID)”: ESSID is the name of thenetwork to which one desires to connect. It is similar to SSID but amore extended concept.

“Basic service set identifier (BSSID)”: BSSID consisting of 48bits isused to distinguish a specific BSS. In the case of an infrastructure BSSnetwork, the BSSID may be medium access control (MAC) of the APequipment. For an independent BSS or ad hoc network, the BSSID may begenerated with any value.

The charging station may include at least one GA and at least one GAcontroller configured to manage the at least one GA. The GA may includeat least one wireless communication device. The charging station mayrefer to a place or location having at least one GA, which is installedin a home, office, public place, road, parking area, etc.

According to exemplary embodiments of the present disclosure, “rapidcharging” may refer to a method of directly converting AC power of apower system to direct current (DC) power, and supplying the convertedDC power to a battery mounted on an EV. In particular, a voltage of theDC power may be DC 500 volts (V) or less.

According to exemplary embodiments of the present disclosure, “slowcharging” may refer to a method of charging a battery mounted on an EVusing AC power supplied to a general home or workplace. An outlet ineach home or workplace, or an outlet disposed in a charging stand mayprovide the AC power, and a voltage of the AC power may be AC 220V orless. The EV may further include an on-board charger (OBC) configured toboost the AC power for the slow charging, convert the AC power to DCpower, and supply the converted DC power to the battery.

According to exemplary embodiments of the present disclosure, afrequency tuning may be used for performance optimization. Inparticular, the frequency tuning may be performed by a supply device andmay not be performed by an EV device. Additionally, it may be requiredfor all the supply devices to provide the frequency tuning over a fullrange. An electric vehicle power controller (EVPC) may operate in afrequency range between about 81.38 kHz and 90.00 kHz. A nominalfrequency (hereinafter, referred to as a target frequency, a designfrequency, or a resonance frequency) for the magnetic field wirelesspower transfer (MF-WPT) may be about 85 kHz. The power supply circuitsmay provide the frequency tuning.

Hereinafter, exemplary embodiments of the present disclosure will beexplained in detail by referring to accompanying figures.

FIG. 1 is a conceptual diagram illustrating a concept of a wirelesspower transfer (WPT) to which exemplary embodiments of the presentdisclosure are applied.

As shown in FIG. 1, a WPT may be performed by at least one component ofan electric vehicle (EV) 10 and a charging station 20, and may be usedfor wirelessly transferring power to the EV 10. Here, the EV 10 may beusually defined as a vehicle supplying an electric power stored in arechargeable energy storage including a battery 12 as an energy sourceof an electric motor which is a power train system of the EV 10.

However, the EV 10 according to exemplary embodiments of the presentdisclosure may include a hybrid electric vehicle (HEV) having anelectric motor and an internal combustion engine together, and mayinclude not only an automobile but also a motorcycle, a cart, a scooter,and an electric bicycle. Additionally, the EV 10 may include a powerreception pad 11 including a reception coil for charging the battery 12wirelessly and may include a plug connection for conductively chargingthe battery 12. In particular, the EV 10 configured for conductivelycharging the battery 12 may be referred to as a plug-in electric vehicle(PEV).

Here, the charging station 20 may be connected to a power grid 30 or apower backbone, and may provide an alternating current (AC) power or adirect current (DC) power to a power transmission pad 21 including atransmission coil through a power link. Additionally, the chargingstation 20 may be configured to communicate with an infrastructuremanagement system or an infrastructure server that manages the powergrid 30 or a power network via wired/wireless communications, andperform wireless communications with the EV 10. The wirelesscommunications may be Bluetooth, ZigBee, cellular, wireless local areanetwork (WLAN), or the like. For example, the charging station 20 may belocated at various places including a parking area attached to the ahouse, a parking area for charging an EV at a gas station, a parkingarea at a shopping center or a workplace.

A process of wirelessly charging the battery 12 of the EV 10 may beginwith first disposing the power reception pad 11 of the EV 10 in anenergy field generated by the power transmission pad 21, and couplingthe reception coil and the transmission coil with each other. Anelectromotive force may be induced in the power reception pad 11 as aresult of the interaction or coupling, and the battery 12 may be chargedby the induced electromotive force.

The charging station 20 and the transmission pad 21 may be referred toas a ground assembly (GA) in whole or in part, where the GA may refer tothe previously defined meaning. All or part of the internal componentsand the reception pad 11 of the EV 10 may be referred to as a vehicleassembly (VA), in which the VA may refer to the previously definedmeaning. The power transmission pad or the power reception pad may beconfigured to be non-polarized or polarized.

When a pad is non-polarized, one pole is disposed in a center of the padand an opposite pole is disposed in an external periphery. Inparticular, a flux may be formed to exit from the center of the pad andreturn at all to external boundaries of the pad. When a pad ispolarized, a respective pole may be disposed at either end portion ofthe pad. In particular, a magnetic flux may be formed based on anorientation of the pad. In the present disclosure, the transmission pad21 or the reception pad 11 may collectively be referred to as a“wireless charging pad”.

FIG. 2 is a conceptual diagram illustrating a WPT circuit according toexemplary embodiments of the present disclosure.

As shown in FIG. 2, a schematic configuration of a circuit in which aWPT is performed in an EV WPT system is shown. The left side of FIG. 2may be interpreted as expressing all or part of a power source V_(src)supplied from the power network, the charging station 20, and thetransmission pad 21 in FIG. 1, and the right side of FIG. 2 may beinterpreted as expressing all or part of the EV including the receptionpad and the battery.

First, the left-side circuit of FIG. 2 may provide an output powerP_(src) that corresponds to the power source V_(src) supplied from thepower network to a primary-side power converter. The primary-side powerconverter may be configured to supply an output power P₁ converted fromthe output power P_(src) through frequency-converting andAC-to-DC/DC-to-AC converting to generate an electromagnetic field at adesired operating frequency in a transmission coil L₁.

In particular, the primary-side power converter may include an AC/DCconverter configured to convert the power P_(src) which is an AC powersupplied from the power network into a DC power, and a low-frequency(LF) converter configured to convert the DC power into an AC powerhaving an operating frequency suitable for wireless charging. Forexample, the operating frequency for wireless charging may be determinedto be within about 79 to 90 kHz.

The power P₁ output from the primary-side power converter may besupplied again to a circuit including the transmission coil L₁, a firstcapacitor C₁ and a first resistor R₁. In particular, a capacitance ofthe first capacitor C₁ may be determined as a value to have an operatingfrequency suitable for charging together with the transmission coil L₁.The first resistor R₁ may represent a power loss occurred by thetransmission coil L₁ and the first capacitor C₁.

Further, the transmission coil L₁ may be made to have electromagneticcoupling, which is defined by a coupling coefficient m, with thereception coil L₂ so that a power P₂ is transmitted, or the power P₂ isinduced in the reception coil L₂. Therefore, the meaning of powertransfer in the present disclosure may be used together with the meaningof power induction. Still further, the power P₂ induced in ortransferred to the reception coil L₂ may be provided to a secondary-sidepower converter. Particularly, a capacitance of a second capacitor C₂may be determined as a value having an operating frequency suitable forwireless charging together with the reception coil L₂, and a secondresistor R₂ may represent a power loss occurring by the reception coilL₂ and the second capacitor C₂.

The secondary-side power converter may include an AC-to-DC converterconfigured to convert the supplied power P₂ of a specific operatingfrequency to a DC power having a voltage level suitable for the batteryV_(HV) of the EV. The electric power P_(HV) converted from the power P₂supplied to the secondary-side power converter may be output, and thepower P_(HV) may be used for charging the battery V_(HV) disposed in theEV.

The right side circuit of FIG. 2 may further include a switch forselectively connecting or disconnecting the reception coil L₂ with thebattery V_(HV). In particular, resonance frequencies of the transmissioncoil L₁ and the reception coil L₂ may be similar or identical to eachother, and the reception coil L₂ may be positioned near theelectromagnetic field generated by the transmission coil L₁. The circuitof FIG. 2 should be understood as an illustrative circuit for WPT in theEV WPT system used for exemplary embodiments of the present disclosure,and is not limited to the circuit illustrated in FIG. 2.

On the other hand, since the power loss may increase as the transmissioncoil L₁ and the reception coil L₂ are separated by a predetermineddistance, the relative positions of the transmission coil L₁ and thereception coil L₂ may be set. The transmission coil L₁ may be includedin the transmission pad 21 in FIG. 1, and the reception coil L₂ may beincluded in the reception pad 11 in FIG. 1. Additionally, thetransmission coil may be referred to as a GA coil, and the receptioncoil may be referred to as a VA coil. Therefore, position alignmentbetween the transmission pad and the reception pad or position alignmentbetween the EV and the transmission pad will be described below withreference to the drawings.

FIG. 3 is a conceptual diagram for explaining a concept of alignment inan EV WPT according to exemplary embodiments of the present disclosure.

As shown in FIG. 3, a method of aligning the power transmission pad 21and the power reception pad 11 in the EV in FIG. 1 will be described. Inparticular, positional alignment may correspond to the alignment, whichis the above-mentioned term, and thus may be defined as positionalalignment between the GA and the VA, but is not limited to the alignmentof the transmission pad and the reception pad. Although the transmissionpad 21 is illustrated as positioned below a ground surface as shown inFIG. 3, the transmission pad 21 may also be positioned on the groundsurface, or positioned to expose a top portion surface of thetransmission pad 21 below the ground surface.

The reception pad 11 of the EV may be defined by different categoriesbased on heights (defined in the z-direction) measured from the groundsurface. For example, a class 1 for reception pads having a height ofabout 100-150 millimeters (mm) from the ground surface, a class 2 forreception pads having a height of about 140-210 mm, and a class 3 forreception pads having a height of about 170-250 mm may be defined. Thereception pad may support a part of the above-described classes 1 to 3.For example, only the class 1 may be supported according to the type ofthe reception pad 11, or the class 1 and 2 may be supported according tothe type of the reception pad 11. The height of the reception padmeasured from the ground surface may correspond to the previouslydefined term “vehicle magnetic ground clearance.”

Further, the position of the power transmission pad 21 in the heightdirection (i.e., defined in the z-direction) may be determined to bedisposed between the maximum class and the minimum class supported bythe power reception pad 11. For example, when the reception pad supportsonly the class 1 and 2, the position of the power transmission pad 21may be determined between about 100 and 210 mm with respect to the powerreception pad 11.

In addition, a gap between the center of the power transmission pad 21and the center of the power reception pad 11 may be determined to bedisposed within the limits of the horizontal and vertical directions(defined in the x- and y-directions). For example, the gap may bedetermined to be located within ±75 mm in the horizontal direction(defined in the (+y)-direction or in the right direction perpendicularto the vehicle direction), and within ±100 mm in the vertical direction(defined in the (−x)-direction or in a vehicle travelling direction).The relative positions of the power transmission pad 21 and the powerreception pad 11 may be varied in accordance with experimental results,and the numerical values should be understood as exemplary.

Although the alignment between the pads is described on the assumptionthat each of the transmission pad 21 and the reception pad 11 includes acoil, more particularly, the alignment between the pads may refer to thealignment between the transmission coil (or GA coil) and the receptioncoil (or VA coil) which are respectively included in the transmissionpad 21 and the reception pad 11.

Meanwhile, to maximize charging efficiency during wireless charging toan EV (EV wireless charging), low-frequency (LF) signals may be used foralignment between the primary coil (i.e., GA coil) and the secondarycoil (i.e., VA coil). The LF signal is a digitally modulated magneticfield that operates in a low frequency ITU radio band. An LF sensor mayoperate at a fixed frequency within a frequency range of 19 kHz to 300kHz.

In addition, the magnetic field may be generated by at least twoantennas located in the EV. The LF antennas in the EV may be located,for example, in the positions as shown in FIG. 4 below, without beinglimited by the exemplary embodiment. Preferably, the distance betweenthe antennas located in the EV may be maintained at 600 mm.

Additionally, the primary side device may comprise at least two magneticsensors, wherein sensing elements of the magnetic sensor may bepreferably arranged symmetrically.

The magnetic sensors can measure a strength of the magnetic field in thex, y, and z directions. Meanwhile, in the society of automotiveengineers (SAE) standard meetings, considering autonomous drivingtechnology, position alignment techniques using autonomous (or,automatic) parking or remote parking is being studied.

Also, according to ISO 15118-8 that is an EV charging communicationstandard document, when wireless communication for charging an EV isused, communication between an electric vehicle communication controller(EVCC) and a supply equipment communication controller (SECC) conformsto the IEEE 802.11-2012. A required range of a distance between the EVCCand the SECC for a communication channel considered in the wirelesscommunication is 5 m to 30 m for discovery, 10 cm to 5 m for finepositioning (fine alignment), and 5 cm to 5 m for charge control.

Here, the discovery is a step in which an EV searches for a chargingpad, and the EVCC enters a communication region of at least one SECC andconnects with an appropriate SECC. The fine positioning may refer toalignment between primary and EV devices (i.e., coils) for efficientpower transfer in case of WPT, and alignment between connectors of theEV and an EVSE for power transfer in case of an automatic connection forconductive charging. The charge control may be in form of, for example,a power request from the EV to the EVSE.

FIG. 4 is a conceptual diagram illustrating position alignment forwireless charging to which exemplary embodiments of the presentdisclosure are applied.

As shown in FIG. 4, a position alignment method according to anexemplary embodiment of the present disclosure, which is a method formaximizing and/or optimizing the wireless charging efficiency byaligning a primary coil of a GA to a secondary coil of a VA, may beperformed based on measurement of magnetic fields between four antennasANT1, ANT2, ANT3 and ANT4 in the GA side and two antennas ANTa and ANTbin the VA side.

In particular, the VA may include two antennas, and the two antennas maybe disposed one by one (e.g., sequentially) in the left and rightregions of the VA. The left and right regions may refer to regionsdivided into two halves of the VA, and may be left and rightsymmetrically separated regions. When the VA has a rectangularstructure, the two antennas may be disposed at the center of the leftside and the center of the right side respectively of the rectangularstructure, but the structure is not limited to a rectangle because itmay be changed according to a design selection.

Additionally, the two antennas may be disposed in a specific portion ofthe vehicle as connected with the VA, in which case they may be disposedone by one in the left and right regions of the specific portion of thevehicle. The left region and the right region of the specific portion ofthe vehicle may refer to symmetrically separated regions in the specificportion of the vehicle. Alternatively, instead of the left and rightregions of the specific portion of the VA or the vehicle, a front regionand a rear region of the specific portion of the VA or the vehicle maybe used, but are not limited thereto. In other words, two regions thatare symmetrically separated may be generally used. Hereinafter, it willbe assumed that the antennas are disposed in the VA.

The VA or a VA controller may control the antennas and calculateposition difference information between the VA and the GA.

The GA may include four antennas, and the four antennas may be disposedin a first region, a second region, a third region, and a fourth regionof the GA, respectively, and the first, second, third, and fourthregions may refer to a upper left region, a upper right region, a lowerleft region, and a lower right region of the GA, respectively. However,exemplary embodiments of the present disclosure are not limited thereto,and may refer to regions divided from the GA into quadrants to have thesame size. When the GA has a rectangular structure, the four antennasmay be disposed at each corner of the rectangular structure, but thestructure is not limited to a rectangle because it may be changedaccording to a design selection. Additionally, the GA or a GA controllermay also calculate magnetic field measurement values based on magneticfields detected by the four antennas.

Herein, the antenna included in the VA and/or GA may refer to a loopantenna or may refer to a ferrite rod antenna, but is not limitedthereto. The ferrite rod antenna can be used in vehicles, portableradios, and aircraft due to its reduced size, have almost no reflection,and allow for good range control with a gentle reduction in the fieldstrength. Also, the ferrite rod antenna may have a high penetrationrate, require a low quiescent current according to a resonant frequencyinput stage, and may be less susceptible to detuning compared to highfrequencies. However, since the ferrite rod antenna has a very high Qfactor, it is possible to filter some of required signal modulation.

The ferrite rod antenna may refer to an antenna using an LF. A ferriterod loop antenna may be thought of as a special case of conventionalair-core loop antennas. The air-core loop antenna is synonymous with asolenoid. Thus, a magnetic field in the solenoid may be expressed on thebasis of Ampere's law. However, since a medium inside a coil in thesolenoid is air, if the inside medium is a ferrite rod, the ferrite rod,the medium inside the coil, should be reflected. In addition,considering the number of turns of the coil, the radius of the coil, thelength of the coil, etc., the final magnetic field of the LF antenna(i.e., ferrite rod loop antenna) may be expressed by Equation 1 below.

$\begin{matrix}{B = {\frac{\mu_{o}{INa}^{2}}{2\left( {a^{2} + r^{2}} \right)^{3/2}} \approx {\frac{\mu_{o}{INa}^{2}}{2r^{3}}\lbrack{Tesla}\rbrack}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

whereμ₀=magnetic permeability

I=Current [A]

N=Number of turnsa=radius of coil [m]r=distance from coil [m]

Meanwhile, the LF may refer to an LF band using a band of 30 to 300 kHzamong 12 frequency ranges classified by International TelecommunicationUnion (ITU). Table 1 below shows the frequency ranges divided into 12ranges in the ITU.

TABLE 1 Abbreviation Frequency range Wave length range 1 ELF 3~30 Hz100,000~10,000 km 2 SLF 30~300 Hz 10,000~1000 km 3 ULF 300~3000 Hz1000~100 km 4 VLF 3~30 kHz 100~10 km 5 LF 30~300 kHz 10~1 km 6 MF300~3000 kHz 1000~100 m 7 HF 3~30 MHz 100~10 m 8 VHF 30~300 MHz 10~1 m 9UHF 300~3000 MHz 1~0.1 m 10 SHF 3~30 GHz 100~10 mm 11 EHF 30~300 GHz10~1 mm 12 THF 300~3000 GHz 1~0.1 mm

FIGS. 5A and 5B are diagrams illustrating an example of LF antennaalignment between a transmission pad and a reception pad.

As shown in FIGS. 5A and 5B, a (x, y) coordinate system represents acoordinate system for a transmission pad of an EVSE, and a (x′, y′)coordinate system represents a coordinate system of a vehicle (or,reception pad). The antennas of the EVSE side (or, transmission pad) arerepresented by P1, P2, P3 and P4, and are arranged symmetrically in theupper left, upper right, lower left and lower right region of thetransmission pad. The antennas of the vehicle side are represented by V1and V2, and are symmetrically located around the magnetic fieldstructure of the reception pad as shown in FIG. 5A. Meanwhile, in FIG.5B, the vehicle side antennas V1 and V2 are symmetrically positionedaround the magnetic field structure away from the reception pad.

In consideration of such the arrangement, the vehicle side device andthe power supply side device may perform position alignment using the LFsignals.

That is, when the vehicle approaches a specific parking spot forcharging, a frequency for the corresponding parking spot selected by anSECC may be reported to the vehicle through a WLAN link. The vehicle maytransmit a corresponding trigger signal to the power supply side deviceat the selected frequency. The SECC may return a received signalstrength intensity (RSSI) value measured by a sensor to the vehicle. Assuch, a position measurement algorithm may be performed by the vehiclebased on the RSSI value fed back by the power supply side device.

The vehicle (i.e., EV) may request fine positioning using an LF. TheSECC, which receives the request for fine positioning, may request thepower supply side device to turn on a receiver, and inform the vehicleof a frequency to use. The vehicle may turn on a receiver and may startat the specified frequency.

When a driver moves the vehicle to the parking spot, that is, a chargingspot, and the reception coil of the vehicle approaches within 4 m˜6 m ofthe transmission coil of the power supply side, the receiver of thetransmission coil may detect a signal transmitted by the vehicle.

The vehicle may transmit LF signals for positioning to the transmissioncoil, and the SECC may transmit measured raw data to the vehicle througha WLAN link. Based on the measured values, the vehicle may dynamicallycalculate the position of the transmission coil.

As such, according to an exemplary embodiment of the present disclosure,the vehicle may measure the distance between the transmission pad andthe reception pad based on the RSSI received from the power supplydevice.

Distance measurement based on RSSI may be expressed according toEquation 2 below.

$\begin{matrix}{d = {{10\frac{{- {RSSI}} + A_{r}}{10^{n}}\mspace{14mu} {or}\mspace{14mu} d} = {{\frac{\lambda}{4\pi} \cdot 10^{\frac{L}{20}}} = {\frac{c}{4\pi \; f} \cdot 10^{\frac{L}{20}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Here, d denotes a distance, n denotes a signal propagation constant, andA_(r) denotes a RSSI value per meter. Further, λ denotes a wavelength ofpropagation, c denotes a speed of propagation, f denotes a frequency ofradio wave, and L denotes propagation path loss (transmitting signalstrength−received signal strength)

The position alignment for wireless charging may be accomplished usingLF signals and magnetic vectoring. The magnetic vectoring is a scheme ofmeasuring a distance by detecting weak magnetic fields. For the magneticvectoring, auxiliary coils are wound around three axes (X, Y, Z) on atransmission coil, and auxiliary coils are wound around two axes (X, Y)on a reception coil. That is, the distance is measured by sensing theweak magnetic fields induced in the auxiliary coils.

Meanwhile, recent experiments have reported that precise alignment isdifficult when LF signals and magnetic vectoring are used in the EVwireless charging.

FIG. 6 is a diagram illustrating an error occurring when aligningpositions using LF signals or magnetic vectoring.

A result shown in FIG. 6 is a result of aligning positions by using fourLF antennas or LF sensors in a transmission coil and two LF antennas orLF sensors in a reception coil as defined in the IEC 61980-2 TS standarddocument. The result shown in FIG. 6 indicates that position-relateddata cannot be obtained when a distance between the transmission coiland the reception coil is very near. That is, it can be confirmed thatprecise alignment is difficult when aligning the positions using the LFsignals and the magnetic vectoring.

This is most likely due to the use of a weak magnetic field withmagnetic field strength of tens of nT, which is used when measuring thedistance by using the LF signals or the magnetic field strengths of theauxiliary coils for the magnetic vectoring. That is, in case of usingthe weak magnetic fields, if the distance between the transmission coiland the reception coil is very near (e.g., 0 to 0.5 m), the weakmagnetic field differences between the auxiliary coils (or auxiliaryantennas) of the transmission coil and the auxiliary coils (or auxiliaryantennas) of the reception coil becomes difficult to be distinguished,so that it is difficult to accurately determine the distance between thetransmission coil and the reception coil.

In addition, according to the IEC 61980-2 TS standard document, four LFantennas or LF sensors are disposed on a transmission coil, and two LFantennas or LF sensors are disposed on a reception coil to determineposition information by using a weak magnetic field. However, asdescribed above, there may be difficulty in determining the positioninformation at a very short distance by using such the structure.

Therefore, the present disclosure proposes a method for enabling precisealignment at a very near distance (e.g., 0 to 0.5 m) when aligning thepositions using the LF signals for EV wireless charging.

The international standard for EV wireless charging does not clearlydescribe a signal transmission process of antennas and sensors for LFsignals.

According to an exemplary embodiment of the present disclosure, when amagnetic field is transmitted from the LF antennas of the receptioncoil, a magnetic flux density may be changed until the alignment iscompleted without using only the maximum magnetic flux density. Throughthis, the LF antenna (or LF sensor) of the transmission coil canrecognize the magnetic flux density of the LF antenna of the receptioncoil even at a very short distance (e.g., 0 to 0.5 m).

According to an exemplary embodiment of the present disclosure, amagnetic flux density for a first LF signal emitted from the LF antennamay be set to the maximum value, and a magnetic flux density for asecond LF signal emitted from the LF antenna may be set to the minimumvalue. The two signals are configured in one package, and the configuredsignals may transmitted to the LF antenna (or LF sensor) of thetransmission coil.

When the reception coil approaches the transmission coil and thedistance between the two coils is within a very near distance (e.g., 0to 0.5 m), for the magnetic flux density of the LF receiving antennalocated in the transmission coil, a value measured at a first time pointmay be compared with a value measured at a second time point in order toefficiently perform a position measurement algorithm. According to anexemplary embodiment of the present disclosure, when a differencebetween the two values does not exceed a predetermined threshold, thecorresponding data (e.g., the magnetic flux density measured at thefirst time point or the magnetic flux density measured at the secondtime point) may be excluded from the position measurement algorithm.Then, a calculation on the distance between the transmission pad and thereception pad may be performed using only significant data on themagnetic flux densities of the LF antennas. In this case, a method usingRSSI may be used for distance measurement.

Here, a time interval between a transmission time point of the firstsignal whose magnetic flux density is set to the maximum value and atransmission time point of the second signal whose magnetic flux densityis set to the minimum value may be very short. Further, a time intervalbetween the first package and the second package subsequent to the firstpackage may be set longer than the time interval between the firstsignal and the second signal in the same package.

When the reception coil approaches the center of the transmission coilto maximize charging efficiency and is located within a very neardistance (e.g., 0 to 0.5 m), the magnetic flux density measured by theLF antenna or the LF sensor of the transmission coil may be almostunchanged. Thus, in an exemplary embodiment of the present disclosure,for effective calculation for a distance measurement algorithm, magneticflux densities at different time points for each LF antenna of thetransmission coil may be compared, and when a difference thereof doesnot exceed a predetermined threshold, the corresponding data may beexcluded from data for the position measurement algorithm.

Meanwhile, a method of measuring a distance by analyzing the magneticfields due to the LF signals, which is described in the EV wirelesscharging related standard document, uses a formula as shown in equationsbelow.

For example, the magnetic flux densities detected by the LF antennas ofthe transmission coil that receive the magnetic field transmitted by theLF antenna α of the reception coil at time t0 may be expressed as shownin Equation 3 below.

B (LF antenna A, t0)= BLFAAy ,t0· BLFAαy ,t0

B (LF antenna B, t0)= BLFABy ,t0· BLFAαy ,t0

B (LF antenna C, t0)= BLFACy ,t0· BLFAαy ,t0

B (LF antenna D, t0)= BLFADy ,t0· BLFAαy ,t0   [Equation 3]

In addition, the magnetic flux densities detected by the LF antennas(i.e., LF antenna A, LF antenna B, LF antenna C, LF antenna D) of thetransmission coil that receive the magnetic field transmitted by the LFantenna β of the reception coil at time t1 may be expressed as shown inEquation 4 below.

B (LF antenna A, t1)= BLFAAy ,t1· BLFAβy ,t1

B (LF antenna B, t1)= BLFABy ,t1· BLFAβy ,t1

B (LF antenna C, t1)= BLFACy ,t1· BLFAβy ,t1

B (LF antenna D, t1)= BLFADy ,t1· BLFAβy ,t1   [Equation 4]

Therefore, equations for final RSSIs calculated by the LF antennas ofthe reception coil at the times t0 and t1 may be summarized as shown inEquation 5 below.

RSSI ( B (LF antenna A, t0), B (LF antenna B, t0), B (LF antenna C, t0),B (LF antenna D, t0))

RSSI ( B (LF antenna A, t1), B (LF antenna B, t1), B (LF antenna C, t1),B (LF antenna D, t1))   [Equation 5]

Eventually, the LF antenna or LF sensor of the transmission coilreceives all the magnetic flux densities transmitted by the LF antennaof the reception coil. However, since the LF antenna of the receptioncoil emits the maximum magnetic flux density, the LF transmitters of thereception coils cannot be distinguished at a very near distance (e.g., 0to 0.5 m).

According to an exemplary embodiment of the present disclosure, when amagnetic field is transmitted from the LF antennas of the receptioncoil, a magnetic flux density may be changed until the alignment iscompleted without using only the maximum magnetic flux density, so thatthe LF antenna (or LF sensor) of the transmission coil can recognize themagnetic flux density of the LF antenna of the reception coil even at avery short distance (e.g., 0 to 0.5 m).

That is, a magnetic flux density for a first LF signal emitted from theLF antenna of the reception coil may be set to the maximum value, and amagnetic flux density for a second LF signal emitted from the LF antennaof the reception coil may be set to the minimum value. The two signalsare configured in one package, and the configured signals maytransmitted to the LF antenna (or LF sensor) of the transmission coil.Here, a time interval between a transmission time point of the firstsignal whose magnetic flux density is set to the maximum value and atransmission time point of the second signal whose magnetic flux densityis set to the minimum value may be very short. Also, a time intervalbetween the first package and the second package subsequent to the firstpackage may be set longer than the time interval between the firstsignal and the second signal in the same package.

In summary, when the reception coil approaches the center of thetransmission coil to maximize charging efficiency and comes within avery near distance (e.g., 0 to 0.5 m), the magnetic flux densitymeasured by the LF antenna or the LF sensor of the transmission coil maybe almost unchanged. Thus, in an exemplary embodiment of the presentdisclosure, for effective calculation for a distance measurementalgorithm, magnetic flux densities at different time points for each LFantenna of the transmission coil may be compared, and when a differencethereof does not exceed a predetermined threshold, the correspondingdata may be excluded from data for the position measurement algorithm.

FIG. 7A is a diagram describing magnetic flux densities when atransmission coil and a reception coil are located within a very shortdistance according to an exemplary embodiment of the present disclosure.

In this exemplary embodiment, a case where the LF transmitters of thereception coil emit the maximum value of the LF magnetic field at anarbitrary time point will be described. In this case, the maximum valuemay mean a maximum value within a preconfigured range of a magneticfield that the LF antenna of the reception pad can use for emission tothe LF antenna or sensor of the transmission pad during positionalignment.

For example, the magnetic flux densities detected by the LF antennas(i.e., LF antenna A, LF antenna B, LF antenna C, LF antenna D) of thetransmission coil that receive the maximum value of the magnetic fieldemitted by the LF antenna α of the reception coil at time t0 may beexpressed as shown in Equation 6 below.

B (LF antenna A, t0)= BLFAA, t0·BLFAα(max), t0

B (LF antenna B, t0)= BLFAB, t0·BLFAα(max), t0

B (LF antenna C, t0)= BLFAC, t0·BLFAα(max), t0

B (LF antenna DA, t0)= BLFAD, t0·BLFAα(max), t0   [Equation 6]

In addition, the magnetic flux densities detected by the LF antennas ofthe transmission coil that receive the maximum value of the magneticfield emitted by the LF antenna β of the reception coil at time t1 maybe expressed as shown in Equation 7 below.

B (LF antenna A, t1)= BLFAA, t1·BLFAβ(max), t1

B (LF antenna B, t1)= BLFAB, t1·BLFAβ(max), t1

B (LF antenna C, t1)= BLFAC, t1·BLFAβ(max), t1

B (LF antenna D, t1)= BLFAD, t1·BLFAβ(max), t10   [Equation 7]

Here, t0 is a time point at which each LF antenna of the transmissioncoil receives the magnetic field emitted by the LF antenna α of thereception coil, and t1 is a time point at which each LF antenna of thetransmission coil receives the magnetic field emitted by the LF antennaβ of the reception coil. Therefore, t0 and t1 may be different values,or may be the same value.

FIG. 7B is a diagram describing magnetic flux densities when atransmission coil and a reception coil are located within a very shortdistance according to another exemplary embodiment of the presentdisclosure.

In this exemplary embodiment, a case where the LF transmitters of thereception coil emit the minimum value of the LF magnetic field at anarbitrary time point will be described.

Also, the magnetic flux densities detected by the LF antennas (i.e., LFantenna A, LF antenna B, LF antenna C, LF antenna D) of the transmissioncoil that receive the minimum value of the magnetic field emitted by theLF antenna α of the reception coil at time t2 may be expressed as shownin Equation 8 below.

B (LF antenna A, t2)= BLFAA, t2·BLFAα(min), t2

B (LF antenna B, t2)= BLFAB, t2·BLFAα(min), t2

B (LF antenna C, t2)= BLFAC, t2·BLFAα(min), t2

B (LF antenna D, t2)= BLFAD, t2·BLFAα(min), t2  [Equation 8]

In addition, the magnetic flux densities detected by the LF antennas ofthe transmission coil that receive the minimum value of the magneticfield emitted by the LF antenna β of the reception coil at time t3 maybe expressed as shown in Equation 9 below.

B (LF antenna A, t3)= BLFAA, t3·BLFAβ(min), t3

B (LF antenna B, t3)= BLFAB, t3·BLFAβ(min), t3

B (LF antenna C, t3)= BLFAC, t3·BLFAβ(min), t3

B (LF antenna D, t3)= BLFAD, t3·BLFAβ(min), t3   [Equation 9]

Here, t2 is a time point at which each LF antenna of the transmissioncoil receives the magnetic field emitted by the LF antenna α of thereception coil, and t3 is a time point at which each LF antenna of thetransmission coil receives the magnetic field emitted by the LF antennaβ of the reception coil. Therefore, t2 and t3 may be different values,or may be the same value.

Finally, equations for RSSIs at each LF antenna (or, sensor) of thetransmission coil, which are for measuring the distance between thetransmission pad and the reception pad, may be summarized as shown inEquation 10 below.

RSSI {( B (LF antenna A, t0), B (LF antenna B, t0), B (LF antenna C,t0), B (LF antenna D, t0)), ( B (LF antenna A, t1), B (LF antenna B,t1), B (LF antenna C, t1), B (LF antenna D, t1))}

RSSI {( B (LF antenna A, t2), B (LF antenna B, t2), B (LF antenna C,t2), B (LF antenna D, t2)), ( B (LF antenna A, t3), B (LF antenna B,t3), B (LF antenna C, t3), B (LF antenna D, t3))}  [Equation 10]

FIG. 8 is a diagram describing magnetic flux densities when a distancebetween a transmission coil and a reception coil is changed within avery close distance according to an exemplary embodiment of the presentdisclosure.

As shown in FIG. 8, when the transmission coil and the reception coilare in close proximity to each other, the maximum magnetic flux densityemitted from the LF antenna of the reception coil for times t0 to t1 maybe compared with the minimum magnetic flux density emitted by the LFantenna of the reception coil for times t2 to t3. As a result of thecomparison, when a difference between the two values is less than athreshold, the corresponding magnetic flux density values may beexcluded from data for the position measurement algorithm.

This may be expressed as shown in Equation 11 below.

RSSI {( B (LF antenna A, t0), B (LF antenna B, t0),

, B (LF antenna D, t0)), ( B (LF antenna A, t1), B (LF antenna B, t1),

, B (LF antenna D, t1))}

RSSI {( B (LF antenna A, t2), B (LF antenna B, t2),

, B (LF antenna D, t2)), ( B (LF antenna A, t3), B (LF antenna B, t3),

, B (LF antenna D, t3))}  [Equation 11]

FIGS. 9A to 9C are sequence charts illustrating operations of a positionalignment method according to an exemplary embodiment of the presentdisclosure.

The position alignment method illustrated in FIGS. 9A to 9C may includeoperations of an EVSE and a vehicle EV and a transmission and receptionprocedure performed therebetween.

As shown in FIG. 9A, the position alignment method according to thepresent disclosure may start with an initial detection procedure S900 ofthe LF magnetic field.

In the initial detection procedure of the LF magnetic field (S900), a VA100 may emit an initial magnetic field using the LF transmitter, and anEVCC 110 of the vehicle may request a WPT initial pairing to an SECC210. The SECC 210 notified that the LF signal is detected through the GAmay transmit a GA LF detect data request to the EVCC 110 of the vehiclein response to the request of the initial pairing from the EVCC 110.

That is, in the initial detection procedure of the LF magnetic field(S900), the VA may initially emit an LF magnetic field through at leastone LF transmitter, and a GA may receive the magnetic field emitted fromthe at least one LF transmitter of the VA.

The vehicle receiving the GA LF detect data request may perform analignment procedure (S910). Here, the VA 100 may emit a magnetic fieldhaving a first magnetic flux density through at least one LFtransmitter. The at least one LF transmitter may be two, for example,antenna α and antenna β. The antenna α may emit a magnetic field suchthat the corresponding magnetic flux density becomes the maximum valuewithin a configuration range at time t0, and the antenna β may emit amagnetic field such that the corresponding magnetic flux density becomesthe maximum value within a configuration range at time t1.

The VA 100 may then emit a magnetic field having a second magnetic fluxdensity through at least one LF transmitter. Likewise, the at least oneLF transmitters may be two, for example antenna α and antenna β. Theantenna α may emit a magnetic field such that the corresponding magneticflux density becomes the minimum value within a configuration range attime t2, and the antenna β may emit a magnetic field such that thecorresponding magnetic flux density becomes the minimum value within aconfiguration range at time t3.

As shown in FIG. 9B, the GA 200 of the EVSE may detect the magneticfield emitted by the at least one LF transmitter of the VA (S920). Inthe magnetic field detection step S920 by the GA 200, the GA 200 maymeasure a first magnetic flux density for the magnetic field emitted byat least one LF transmitter through at least one LF receiver. In thiscase, the at least one LF receiver may include four antennas, forexample, LF antenna A, LF antenna B, LF antenna C, and LF antenna D. Inthis case, each of LF antenna A, LF antenna B, LF antenna C, and LFantenna D may detect the magnetic fields emitted by the transmitter αand the transmitter β. Here, the first magnetic flux density may be themaximum value of the magnetic flux density for the magnetic fieldtransmitted by the at least one LF transmitter.

The GA 200 may also measure a second magnetic flux density for themagnetic field emitted by at least one LF transmitter through at leastone LF receiver. Also in this case, the at least one LF receiver mayinclude four antennas, for example, LF antenna A, LF antenna B, LFantenna C, and LF antenna D. That is, each of LF antenna A, LF antennaB, LF antenna C, and LF antenna D may detect the magnetic fields emittedby the transmitter α and the transmitter β. Here, the second magneticflux density may be the minimum value of the magnetic flux density forthe magnetic field transmitted by the at least one LF transmitter.

Then, the GA 200 may configure a received signal measurement based on aresult of comparing the first magnetic flux density and the secondmagnetic flux density, and the received signal measurement may be areceived signal strength indicator (RSSI).

That is, it may be determined whether a difference between the firstmagnetic flux density and the second magnetic flux density is greaterthan or equal to a threshold, and when the difference between the firstmagnetic flux density and the second magnetic flux density is less thanthe threshold, the first magnetic flux density and the second magneticflux density may be excluded from the received signal measurement. Inother words, the received signal measurement may include only magneticflux density related data in which the difference between the firstmagnetic flux density and the second magnetic flux density is greaterthan or equal to the threshold.

The GA 200 may provide the configured received signal measurement to thevehicle 100 through the SECC 210 (S925).

As shown in FIG. 9C, the EV 100 receiving the received signalmeasurement may calculate a distance between the VA and the GA based onthe received signal measurement, and the vehicle may execute automaticparking for position alignment according to the calculated distance(S930).

On the other hand, in the above-described exemplary embodiment, thedistance between the VA and the GA is calculated on the vehicle side byusing the measured magnetic field related values. However, thecalculation of the distance may be calculated by the EVSE according toanother exemplary embodiment of the present disclosure. In this case,the EVSE may provide the calculated distance to the vehicle so that thedistance can be used for position alignment by the vehicle.

FIG. 10 is a block diagram illustrating a position measurement apparatusaccording to an exemplary embodiment of the present disclosure.

As shown in FIG. 10, a position alignment apparatus 100 according to anexemplary embodiment of the present disclosure may include acommunication unit 110, a processing unit 120, an LF transmission unit130, and at least one LF transmitter 140.

The position measurement apparatus 100 may be a VA or a part of the VA,or may be connected to the VA. That is, the component of the positionmeasurement apparatus 100 is not limited to its name, and it may bedefined by a function. Also, one component constituting the apparatusmay perform a plurality of functions, and a plurality of componentsconstituting the apparatus may perform one function.

The communication unit 110 may include a communication module capable ofcommunicating with an EVSE 200 to be described later. Here, thecommunication module may include a communication module capable ofperforming WIFI communication, and may also include a communicationmodule capable of performing 3G communication and 4G communication, butis not limited thereto. The communication unit 110 may search for aparking space where a GA is located through the communication module,communicate with the EVSE 200 connected to the GA for alignment betweenthe GA and the VA, and receive magnetic field measurements from the EVSE200.

Also, the communication unit 110 may measure at least one of a receivedsignal strength indicator (RSSI), a time of flight (ToF), a timedifference of flight (TDoF), and a time of arrival (ToA), and a timedifference of arrival.

The processing unit 120 may verify whether at least one antennaconnected to the LF transmission unit 130 to be described later isnormally driven, drive the at least one antenna, and perform positionalignment between the transmission pad and the reception pad by usingthe magnetic field measurements received through the communication unit110.

The LF transmission unit 130 may verify whether the connected antenna isnormally driven according to the operation of the processing unit 120,and may drive the at least one transmitter according to the presentdisclosure.

Also, the position measurement apparatus 100 according to an exemplaryembodiment of the present disclosure may include at least one processorand a memory storing at least one instruction for executing theabove-described operations through the at least one processor. Here, theprocessor may execute the at least one instruction stored in the memory,and may be a central processing unit (CPU), a graphics processing unit(GPU), or a dedicated processor executing the methods according to theexemplary embodiments of the present disclosure. The memory may becomprised of a volatile storage medium and/or a nonvolatile storagemedium, and may be comprised of a read only memory (ROM) and/or a randomaccess memory (RAM).

Here, the at least one instruction may be configured the processor toemit a magnetic field having a first magnetic flux density through atleast one LF transmitter; emit a magnetic field having a second magneticflux density through the at least one LF transmitter; receive a receivedsignal measurement from the GA that detects the first magnetic fluxdensity and the second magnetic flux density; and calculate a distancebetween the VA and the GA based on the received signal measurement.

The first magnetic flux density may be a maximum magnetic flux densityfor the magnetic field emitted from the at least one LF transmitter, andthe second magnetic flux density may be a minimum magnetic flux densityfor the magnetic field emitted from the at least one LF transmitter.

The received signal measurement may include only data related to thefirst magnetic flux density and the second magnetic flux density whichhave a difference equal to or greater than a threshold.

The received signal measurement may be an RSSI, and the first magneticflux density and the second magnetic flux density may be emitted atdifferent time points.

The first magnetic flux density and the second magnetic flux density maybe measured for each magnetic field emitted by the at least one LFtransmitter by each of at least one LF receiver of the EVSE.

FIG. 11 is a block diagram illustrating an EVSE according to anexemplary embodiment of the present disclosure.

As shown in FIG. 11, an EVSE 200 according to an exemplary embodiment ofthe present disclosure may include a communication unit 210, aprocessing unit 220, and an LF reception unit 230. The EVSE 200 mayinclude a GA, or may be a GA itself. That is, the component of the EVSE200 is not limited to its name, and it may be defined by a function.Also, one component constituting the apparatus may perform a pluralityof functions, and a plurality of components constituting the apparatusmay perform one function.

The communication unit 210 may include a communication module capable ofcommunicating with the position measurement apparatus 100. Here, thecommunication module may include a communication module capable ofperforming WIFI communication, and may also include a communicationmodule capable of performing 3G communication and 4G communication, butis not limited thereto.

Also, the communication unit 210 may be connected to the positionmeasurement apparatus 100 for alignment between the GA and the VA, andmay transmit measurements of received signals, which are configuredaccording to the present disclosure, to the position measurementapparatus 100.

The processing unit 220 may derive the magnetic field measurements basedon information on magnetic fields detected by the LF reception unit 230to be described later. Here, the information on the magnetic fields mayexist for each antenna. The processing unit 220 may provide the magneticfield measurements to the communication unit 210.

The LF reception unit 230 may be connected to a plurality of, forexample, four receiving antennas located in the GA, and obtaininformation on magnetic fields emitted by the two transmitters of theposition measurement apparatus 100, which are detected by the fourreceiving antennas. The LF reception unit 230 may provide the processingunit 220 with the obtained information on the magnetic fields.

Also, the EVSE 200 according to an exemplary embodiment of the presentdisclosure may include at least one processor and a memory storing atleast one instruction for executing the above-described operationsthrough the at least one processor. Here, the processor may execute theat least one instruction stored in the memory, and may be a centralprocessing unit (CPU), a graphics processing unit (GPU), or a dedicatedprocessor executing the methods according to the exemplary embodimentsof the present disclosure. The memory may be comprised of a volatilestorage medium and/or a nonvolatile storage medium, and may be comprisedof a read only memory (ROM) and/or a random access memory (RAM).

The at least one instruction may be configured the processor to measure,through at least one LF receiver of the GA, a first magnetic fluxdensity for a magnetic field emitted from at least one LF transmitter ofa VA; measure, through the at least one LF receiver, a second magneticflux density for a magnetic field emitted from the at least one LFtransmitter; configure a received signal measurement based on acomparison result of the first magnetic flux density and the secondmagnetic flux density; and provide the configured received signalmeasurement to a vehicle.

While some aspects of the present disclosure have been described in thecontext of an apparatus, it may also represent a description accordingto a corresponding method, wherein the block or apparatus corresponds toa method step or a feature of the method step. Similarly, aspectsdescribed in the context of a method may also be represented by featuresof the corresponding block or item or corresponding device. Some or allof the method steps may be performed by (or using) a hardware devicesuch as, for example, a microprocessor, a programmable computer, or anelectronic circuit. In various exemplary embodiments, one or more of themost important method steps may be performed by such an apparatus.

In exemplary embodiments, a programmable logic device (e.g., a fieldprogrammable gate array (FPGA)) may be used to perform some or all ofthe functions of the methods described herein. In addition, the FPGA mayoperate in conjunction with a microprocessor to perform one of themethods described herein. Generally, the methods are preferablyperformed by some hardware device.

While the exemplary embodiments of the present disclosure and theiradvantages have been described in detail, it should be understood thatvarious changes, substitutions, and alterations may be made hereinwithout departing from the scope of the present disclosure.

What is claimed is:
 1. A position alignment method performed by a groundassembly (GA) for wireless power transfer, the position alignment methodcomprising: measuring, through at least one low frequency (LF) receiverof the GA, a first magnetic flux density for a magnetic field emittedfrom at least one LF transmitter of a vehicle assembly (VA); measuring,through the at least one LF receiver, a second magnetic flux density fora magnetic field emitted from the at least one LF transmitter;configuring a received signal measurement based on a comparison resultof the first magnetic flux density and the second magnetic flux density;and providing the configured received signal measurement to a vehicle.2. The position alignment method according to claim 1, wherein the firstmagnetic flux density is a maximum magnetic flux density for themagnetic field emitted from the at least one LF transmitter, and thesecond magnetic flux density is a minimum magnetic flux density for themagnetic field emitted from the at least one LF transmitter.
 3. Theposition alignment method according to claim 1, wherein the configuringof the received signal measurement comprises: determining whether adifference between the first magnetic flux density and the secondmagnetic flux density is greater than or equal to a threshold; andexcluding the first magnetic flux density and the second magnetic fluxdensity from the received signal measurement when the difference betweenthe first magnetic flux density and the second magnetic flux density isless than the threshold.
 4. The position alignment method according toclaim 1, wherein the received signal measurement is a received signalstrength indicator (RSSI).
 5. The position alignment method according toclaim 1, wherein the first magnetic flux density and the second magneticflux density are measured at different time points by the at least oneLF receiver.
 6. The position alignment method according to claim 1,further comprising initially detecting a magnetic field emitted from theat least one LF transmitter of the VA.
 7. A position measurement methodperformed by a vehicle assembly (VA) for wireless power transfer, theposition measurement method comprising: emitting a magnetic field havinga first magnetic flux density through at least one low frequency (LF)transmitter; emitting a magnetic field having a second magnetic fluxdensity through the at least one LF transmitter; receiving a receivedsignal measurement from a ground assembly (GA) that detects the firstmagnetic flux density and the second magnetic flux density; andcalculating a distance between the VA and the GA based on the receivedsignal measurement.
 8. The position measurement method according toclaim 7, wherein the first magnetic flux density is a maximum magneticflux density for the magnetic field emitted from the at least one LFtransmitter, and the second magnetic flux density is a minimum magneticflux density for the magnetic field emitted from the at least one LFtransmitter.
 9. The position measurement method according to claim 7,wherein the received signal measurement includes only data related tothe first magnetic flux density and the second magnetic flux densitywhich have a difference equal to or greater than a threshold.
 10. Theposition measurement method according to claim 7, wherein the receivedsignal measurement is a received signal strength indicator (RSSI). 11.The position measurement method according to claim 7, wherein the firstmagnetic flux density and the second magnetic flux density are emittedat different time points.
 12. The position measurement method accordingto claim 7, further comprising initially emitting a magnetic fieldthrough the at least one LF transmitter.
 13. A position measurementapparatus comprising: at least one low frequency (LF) transmitter; acommunication module configured to receive a received signal measurementfrom a ground assembly (GA) that detects the first magnetic flux densityand the second magnetic flux density; and a processor configured tocontrol the LF transmitter to emit a magnetic field having a firstmagnetic flux density and to emit a magnetic field having a secondmagnetic flux density, and calculate a distance between a vehicleassembly (VA) and the GA based on the received signal measurement. 14.The position measurement apparatus according to claim 13, wherein thefirst magnetic flux density is a maximum magnetic flux density for themagnetic field emitted from the at least one LF transmitter, and thesecond magnetic flux density is a minimum magnetic flux density for themagnetic field emitted from the at least one LF transmitter.
 15. Theposition measurement apparatus according to claim 13, wherein thereceived signal measurement includes only data related to the firstmagnetic flux density and the second magnetic flux density which have adifference equal to or greater than a threshold.
 16. The positionmeasurement apparatus according to claim 13, wherein the received signalmeasurement is a received signal strength indicator (RSSI).
 17. Theposition measurement apparatus according to claim 13, wherein the firstmagnetic flux density and the second magnetic flux density are emittedat different time points.
 18. The position measurement apparatusaccording to claim 13, wherein the processor is further configured tocontrol the LF transmitter to initially emit a magnetic field.
 19. Theposition measurement apparatus according to claim 13, wherein the firstmagnetic flux density and the second magnetic flux density are measuredfor each magnetic field emitted by the at least one LF transmitter byeach of at least one LF receiver of an electric vehicle supply equipment(EVSE).
 20. The position measurement apparatus according to claim 13,wherein the LF receiver is an LF antenna or an LF sensor.